Kondo coherence inUBe13: Magnetoresistance at high pressure

We have used resistance measurements at pressures to 95 kbar and magnetic fields to 8 T to probe the establishment of Kondo coherence in the heavy-fermion Kondo lattice ${\mathrm{UBe}}_{13}$. With increasing pressure, the negative magnetoresistance characteristic of noninteracting Kondo impurities evolves into the positive magnetoresistance expected for a coherent Kondo lattice. We show that coherence is established by the suppression of inelastic scattering, over a temperature range which expands as pressure decreases the superconducting transition temperature ${\mathrm{T}}_{\mathrm{c}}$ and increases the Kondo temperature ${\mathrm{T}}_{\mathrm{k}}$.